The invention relates to cleaning and rinsing ware in institutional or industrial automatic warewashing machines. More particularly, the invention involves post detergent treatments and rinsing steps for ware that is first cleaned using alkaline detergents leaving clean ware with an alkaline detergent residue on the ware surface. The clean ware is then processed in a procedure involving a post detergent step and a rinse step. The post detergent step involves the use of an aqueous solution of surfactant or chemical rinse additive or agent that can remove a substantial proportion of previously formed detergent residue. This step can leave some amount, typically a small but measurable proportion of rinse aid, food, surfactant, detergent or a combination residue. A subsequent rinse step uses an aqueous potable rinse or an aqueous dilute solution of food grade surfactant to complete the cleaning method and substantially remove such remaining residue.
The use of automatic warewashing machines to clean and rinse ware has been known for many years. Fernholz et al., U.S. Reissue Pat. Nos. 32,818 and 32,763 disclose the use of solid block alkaline cleaning compositions and subsequently rinsing alkaline residues from clean ware. Commonly, after ware is cleaned using alkaline detergents, the ware is often rinsed using a dilute aqueous solution of a typically synthetic polymeric composition comprising at least a block of ethylene oxide in combination with other moieties in the composition to result in an aqueous composition that can cause the rapid sheeting of the rinse water from ware for the intended purpose of leaving a bright, clean, unspotted product. These polymeric materials are typically called rinse aid agents. When dissolved in water a rinse agent forms a rinse solution or composition that, because of the surface energy of the ware and the relationship between the rinse aid and the surface energy, causes sheeting. Warewashing and rinsing processes have been embodied in a variety of institutional and industrial automatic warewashing machines that have automatic control mechanisms that expose ware to a variety of prescraping, scraping, prerinse, alkaline wash, acid wash, rinse, sanitize, post-sanitize, etc. steps. Particularly in large, high volume, multistep warewashing machines, the sequence of steps can be programmed to achieve a desired result.
A variety of cleaning and rinsing processes are known, including Avram, U.S. Pat. No. 5,879,469, which teaches a warewashing system using a basic aqueous wash followed by an acidic aqueous wash. Howland et al., U.S. Pat. No. 5,448,115, shows that aqueous rinse cycles can be effectively controlled to modify dispensing and timing of cleaning chemicals. Young, Jr. et al., U.S. Pat. No. 5,429,679, shows further control systems and in particular directing rinse water recycle into other washing cycle steps. Steindorf, U.S. Pat. No. 5,447,648, and Baum, U.S. Pat. No. 5,589,099, disclose solid food grade rinse aid compositions and improved synthetic ethylene oxide propylene oxide block copolymer based rinse aids. Groult et al., U.S. Pat. No. 4,501,681, show at Column 8, lines 35-55 and elsewhere, the use of multiple rinse steps. Groult et al. appear to show a process involving a first and second rinse step using rinse water followed by a third rinse step using acid or neutral rinsing agents. Jones et al., U.S. Pat. No. 5,232,622, show two sequential rinse steps (Column 6, lines 49-64). Jones et al. disclose nothing regarding the compositions used in the rinse cycles, however, the cycles likely contain conventional synthetic alkaline oxide based rinse agents.
Haslop et al., U.S. Pat. No. 4,618,446, discloses ingredients for use in spherical liquid detergent compositions. Haslop et al., U.S. Pat. No. 4,793,943, teaches a variety of ingredients useful for making liquid detergent compositions. Akred et al., U.S. Pat. No. 4,871,467, teaches a variety of compositions and materials used to form non sedimenting liquid detergent compositions. Aronson et al., U.S. Pat. No. 5,045,225, teaches a combination of hydrocarbon oils and silicone compositions as antifoam materials. Gentle et al., U.S. Pat. No. 5,073,298, teaches silicone silicate based defoaming compositions. Chun et al., U.S. Pat. No. 5,133,892, teaches machine dishwashing detergent tablets having timed release of enzyme and chlorine bleach and a variety of other ingredients used in making the detergent composition.
Tsukada, Japanese Patent Application Publication Kokai 49-126,703, teaches carbohydrate aliphatic ester rinse agents. Miura et al., Japanese Patent Application Publication Kokai 50-62,211, teaches polyhydric alcohol containing rinse agents. Miura et al., Japanese Patent Application Publication Kokai 51-68,608, teaches polyol aliphatic ester containing rinse agent compositions. Suzuki et al., Japanese Patent Application No. 86-131,272, teaches a rinse agent comprising a polyethoxylated sorbitan fatty acid ester glycerol and a sugar alcohol. Suzuki et al., Japanese Patent Application No. 86-161,193, teaches a similar material. Nantaku, Japanese Patent Application No. 59-187,096, teaches a polyglycerine ester of a C6-8 fatty acid containing rinse agent. Wilson et al., xe2x80x9cRinse Additives for Machine Dishwashingxe2x80x9d, Soap and Chemical Specialties. pp. 48 et seq. (February 1958), discusses the basic technology regarding rinse agent formulation. The use of a rinse composition often remove substantial amounts of alkaline residue but can leave some proportion of food residue and some amount of rinse agent residue.
The use of a food grade rinse aid has attracted increasing attention over recent years. Such surfactants are attractive to people requesting more natural chemical materials in warewashing processes. These food grade rinse aids commonly comprise sucrose fatty acid esters, sorbitan fatty acid esters, glycerol fatty acid esters and other similar materials comprising a natural polyol or polymerized polyol derivatized with one or more fatty acid or other natural hydrophobic moiety. Depending on the nature of the ware, the type and content of soil, the hardness of service water, the temperature of washing, and other variables, a food grade rinse aid often provide a level of rinsing which does not meet or exceed the level of rinsing obtained from synthetic polyalkylene oxide type rinse agents.
While the level of activity of the food grade rinse agent is typically acceptable to most operators, a synthetic polyalkylene oxide rinse aid provide a level of sheeting at an effective concentration that is superior to food grade rinse aids. Further, in many kitchens, a strong desire to use food grade rinse aids in a final stage is evident while the use of a synthetic polyalkylene oxide based rinse aid are not desirable in a final step.
Accordingly, a substantial need exists for warewashing methods that can obtain the advantages of conventional rinsing cycles with desired performance while also obtaining the advantages of food grade rinse aid compositions. Such benefits include clean, well rinsed ware with no residue, spotting or streaking.
We have found improved warewashing methods involving cleaning ware with an alkaline detergent producing clean ware, leaving aqueous alkaline residue, followed by a post detergent regimen. In the post detergent regimen, the clean ware is then contacted with a first aqueous post detergent step using an aqueous composition. The aqueous composition comprises a rinse composition having a rinse agent with a polyalkylene oxide moiety to remove the alkaline residue producing treated ware. The treated ware is then contacted in a rinse step with a rinse composition comprising either a food grade rinse agent or an aqueous or potable water rinse, said aqueous or potable water rinse is substantially free of a synthetic rinse agent, for at least three seconds. To ensure complete sanitization of the ware, a sanitation step is used prior to the post detergent regimen. Such a step can include any technique that reduces the numbers of pathogens to a sanitizing level. Preferably, the method uses a biocide or an elevated aqueous rinse temperature to achieve sanitized ware or both.
Accordingly, the invention is found in a method of cleaning ware involving a first cleaning step using an aqueous alkaline cleaning composition, resulting in cleaned ware having an alkaline residue. The cleaned ware is then contacted with an aqueous composition in post detergent step, the aqueous composition comprising about 10 to 500 ppm, of a synthetic nonionic sheeting agent comprising a polyalkylene oxide moiety, to form treated ware. The method further comprises contacting the treated ware with an aqueous rinse composition; wherein the cleaning method also includes a post detergent sanitizing step.
The invention is also found in a method of cleaning ware involving a first cleaning step using an aqueous alkaline cleaning composition, resulting in cleaned ware having an alkaline residue. The cleaned ware is then contacted with an aqueous composition in a post detergent step, the aqueous composition comprising about 10 to 500 ppm, of a synthetic nonionic sheeting agent comprising a polyalkylene oxide moiety, to form treated ware. The method further comprises contacting the treated ware with an aqueous rinse composition comprising about 1 to 800 ppm of a combination of a food grade sheeting agent and a solubility agent; wherein the cleaning method also includes a post detergent sanitizing step.